Synthesis And Magnetic Properties Of Single Molecule Magnets Based On O-vanillin Schiff Base Ligands

The thesis mainly focused on the synthesis,structures and properties of coordination complexes supported by nitrogen-containing ligands.Twenty-one coordination complexes were synthesized by solvothermal reaction.The magnetic properties of several complexes were investigated.These results were described as follows.Eightisostructuraldinuclearlanthanidecomplexesoftheformula[Ln₂L₂¹?NO₃?₂?C₂H₅OH?₂]?0.5py?Ln=Eu?1?,Gd?2?,Tb?3?,Dy?4?,Ho?5?,Er?6?,Yb?7?,Y?8??have been hydrothermally synthesized by employing a relatively rigid and bulky Schiff base 2-{[?2-hydroxy-3-methoxybenzyl?imino]methyl}naphthalen-1-ol?H₂L¹?as a ligand.The structures of the isomorphous complexes 1-8 were determined by IR,X-ray crystallography and X-ray power diffraction.The direct current magnetic susceptibility data of 2-6 were collected in the temperature range of 300-2 K.Complexes[Dy₂L₂¹?NO₃?₂?C₂H₅OH?₂]?0.5py?4?and[Ho₂L₂¹?NO₃?₂?C₂H₅OH?₂]?0.5py?5?display slow magnetic relaxation behavior.It is worth mentioning that the U_eff for 4 of 66.7 K is a relatively high value among the reported Dy₂ SMMs.This work demonstrates the potential applications of the H₂L¹ ligand in the synthesis of SMMs.Eight isostructural mononuclear transition metal complexes[M?DH₂PIP?Cl₂]?M=Cu?9?,Ni?10?,Mn?11?,Fe?12??,[Cu?DH₂PIP?Br₂]?13?,and[M?DBr₂PIP?Cl₂]?M=Cu?14?,Ni?15?,Mn?16??,supported by two nitrogen-containing heterocyclic ligands2,6-bis?imidazo[1,5-a]pyridin-3-yl?pyridine DH₂PIP?H₂L²?and 2,6-bis?1-bromoimidazo[1,5-a]pyridin-3-yl?pyridine DBr₂PIP?L²?,were synthesized and characterized.The structures of the isomorphous complexes 9-16 were determined by IR,X-ray crystallography and X-ray power diffraction.Because of the potential applications of dichloro coordination compounds as catalysts for olefin polymerization,the catalytic properties of these complexes will be further studied.Two isostructural dinuclear transition metal complexes[Cu₂?L³?₂]?17?and[Ni₂?L³?₂]?18?werehydrothermallyaffordedbyemployingSchiffbase4-??1-hydroxy-2,3-dihydro-1H-inden-2-yl?amino?pent-3-en-2-one?H₂L³?as a ligand.The structures of the isomorphous complexes 17 and 18 were determined by IR,X-ray crystallography and X-ray power diffraction.The direct current magnetic susceptibility data of 17 and 18 were collected in the temperature range of 300-2 K.Ferromagnetic interactions are found for complex 17.Three isostructural Ni₄Ln₂ complexes of formula[Ni₄Ln₂L₄¹?NO₃?₂?OH?₄?C₂H₅OH?₂]?Ln=Nd?19?,Ho?20?,Yb?21??have been hydrothermally synthesized by employing Schiff base 2-{[?2-hydroxy-3-methoxybenzyl?imino]methyl}naphthalen-1-ol?H₂L¹?as the ligand.X-ray crystallography analyses revealed that the metal ions of the complexes are bridged by hydroxyl groups to form defective dicuban-like structures.